Metal-clad electrical switch gear



June 22, 1937. D R DAVlES 2,084,893

METAL-GLAD ELECTRICAL SWITCH GEAR Filed March 1., 1955 a E A;

liiii iijjfi H2 [3 Inventor: David 1Q. Davies,

ttorneg Patented June 22, 1937 UNITED STATES PATENT OFFICE David Reginald Davies, Didsbury, England, assignor to General Electric Company, a corporation of New York Application March 1, 1935, Serial No. 8,866 In Great Britain March 8, 1934 2 Claims.

This invention relates to electrical switchgear and in particular to mechanically operable isolating switches commonly employed in such switchgear to govern the interconnection of the 5 main circuit breaker of the switchgear with the terminal of a conductor, such as a cable end, the circuit of which is to be controlled by the switchgear.

According to the invention an improved construction of isolating switch is provided whereby an incoming conductor may, at will, be connected with the terminal of the circuit breaker, or be connected to ground, or be connected to another conductor independent of the switchgear,

such for instance as the conductor of a testing bushing. The alternative electrical connections of the incoming conductor are efiected by means of a switch blade pivoted on the terminal of the incoming conductor and adapted selectively to 0, make contact with the circuit breaker, or with an earthing terminal, or with another conductor such as a testing conductor, and an aperture or window is provided in the surrounding casing and is so arranged that the switch blade or an associated part is visible when the switch is in H the grounding position. Conveniently the position assumed by the isolating switch blade when it makes contact with the testing bushing conductor is intermediate the positions respectively assumed by the switch blade when it makes contact with the circuit breaker terminal, on the one hand, and the earthing terminal, on the other hand.

This invention will be more fully set forth in the following description referring to the accompanying drawing, and the features of novelty which characterize this invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

In order that the invention may be more clearly understood reference will now be made to the accompanying drawing which illustrates by way of example an application of the invention to an electrical circuit breaker such as is shown in Fig. 3 of my U. S. Patent No. 1,992,024 granted February 19, 1935, and similar references indicate the same or equivalent parts.

Referring to the drawing, the single figure thereof is an elevational view, partly in section,

of electric switchgear embodying my invention.

In the apparatus shown in the drawing the dome-shaped casing 3a which is shown in the prior patent specification is replaced by a casing shaped as shown and the conductor 6 of the 55 prior patent is provided with a condenser bushing 6! and terminates in a pivot 62 which supports a switch blade 63.

The switch blade 63 is positioned by a con trol arm 38 acting through a pair of connecting links 64 and may in a first position be caused to engage the contact jaws 23 which are connected to the circuit breaker, i. e. through the conductor l5 illustrated in the prior patent or the switch blade 83 may in a second position be caused to engage the contact jaws 65 of a test conductor (not shown) or in a third position to engage contact jaws I3 which are grounded through the casing 60. It will be observed that the switch blade 63 has two sets of contact surfaces 66 and 61 respectively of which the surfaces 66 make contact with the contact jaws 23 and 65 whereas the surfaces 61 make contact with the ground connecting contact jaws l3.

In the position shown in full line in the drawing the isolating switch is closed so as to connect the incoming conductor with the circuit breaker, whereas the alternative positions in which the conductor is connected with the test conductor and ground respectively are indicated in chain lines.

In some cases it may be desirable alternatively to connect the test conductor with the circuit breaker. This may be effected by displacing the test conductor and condenser bushing 68 which is suitably supported as illustrated by dowel pins, for example downwards so that the contact jaws 65 may engage with and clamp a contact blade 69 associated with the contact jaws 23 so as to be in connection with the circuit breaker. In order to enable the test conductor and associated condenser bushing 68 to be positioned so as to contact with the blade 69 the bushing is introduced through a hinged door H1 in the casing. The position of the jaws 65 when this connection is effected is indicated in broken line. The door 10 when the testing connection is in use is, of course, open for admitting the testing conductor to the casing 60, the conductor (not shown) being electrically connected to the bushing 68 in any suitable manner.

In order to indicate when the incoming conductor is grounded the switch blade 63 is arranged to assume a vertical position when this occurs and to be visible through a window H in the casing.

The portion of the switch blade which shows through the window is rendered conspicuous and for instance it may be painted distinctively or may carry a reflex button.

It should be understood that my invention is not limited to specific details of construction and arrangement thereof herein illustrated, and that changes and modifications may occur to one skilled in the art without departing from the spirit of my invention.

I claim:

1. Electric switchgear of the metal clad type comprising a circuit breaker, a conductor normally in circuit with said breaker, a casing into which extend bushings connected to said breaker and conductor respectively, an isolating switch pivotally mounted with respect to the aforesaid conductor bushing arranged to coact with contact structure on the aforesaid breaker bushing for electrically isolating and connecting respectively said conductor with respect to said breaker, contact structure connected to said casing arranged to be engaged by said switch for grounding said conductor, a testing conductor bushing supported in said casing, means for obtaining access to said testing bushing through a wall of said casing, and contact structure carried by said last named bushing arranged selectively to be engaged by said isolating switch.

2. Electric switchgear of the metal clad type comprising a circuit breaker, a conductor normally in circuit with said breaker, a casing through the lower walls of which extend bushings connected to said breaker and conductor respectively, an isolating switch pivotally' mounted on the aforesaid conductor bushing arranged to coact with contact structure on the aforesaid breaker bushing, grounding contact struc- 

